>I don't think we have a baseline to compare to.  There are simply too many
variables at work that it is a fool's game trying to make a comparison.
 How do you adjust for each variable?  It's like trying to compare apples
and oranges.

Perhaps you missed my point.  I'm curious as to the innate potential of
healthy colonies to survive the winter--prior to varroa and the other
factors that you mentioned.  I've now scoured the old literature, and found
that colonies often survived quite well.  So the old 5-10% expected winter
loss rate appears to be valid, with higher loss rates associated with poor
fall forage, severe winter weather, or lack of wrapping in very cold
climates.

Obviously, all the factors that you mentioned would be expected to have
negative effects.  But the baseline appears today to remain the same.  Many
beekeepers who practice excellent husbandry still report keeping winter
loss rates down in the single digits.  So the question to me is *exactly*
which of those variables that you mentioned, as well as others (such as the
introduction of Nosema ceranae or the neonicotinoids) are involved in
today's higher winter loss rates.


-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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